The present invention relates to an electropneumtic position regulator.
In particular, the invention relates to an electropneumatic position regulator having a current/pressure transducer which has, as electric input, at least one coil which is fed with a current (setting signal), as well as a permanent magnet the relative position of which is variable as a function of the current for the adjustment of a nozzle/impact-plate arrangement of a pneumatic system, for a pneumatic setting device which is connected with the nozzle/impact-plate arrangement and which has a stroke output, and having a position return-report device between the path output and the transducer.
Such electropneumatic position regulators are intended to control the setting stroke of a pneumatic setting device, which is also known as a setting armature or servomotor, proportional to an electric input signal, i.e. a current. The setting device can, for instance, be used in accordance with the setting stroke, to adjust a valve with which a pressure, a flow, a temperature or other variables can be regulated.
One known electropneumatic regulator in a pressure system has, connected with an electric measurement transducer, a negative-feedback dc-voltage amplifier as well as a current/pressure transducer which controls the setting pressure of a pneumatic system for the actuating of the setting device (W. Oppelt, Kleines handbuch technischer Regelvorgange [Brief Manual of Technical Control Processes], 1972, page 354, FIG. 28.19). In detail, the known current/pressure transducer is developed with a moving-coil system in which a moving coil is movably mounted by means of a balance arm opposite a fixed permanent magnet. One end of the balance arm is developed as impact plate facing a pneumatic nozzle which is fed with compressed air via a throttle of a pneumatic system. The pressure upstream of the throttle is adjusted by the force produced with the moving coil system corresponding to the current, which force affects the distance between the impact plate and the pneumatic nozzle. The displacement of the stroke by the pneumatic setting device arranged in the pneumatic system is effected corresponding to the pneumatic pressure. The stroke is transmitted, by means of a spring acting on a spindle of the setting device as opposing force to the balance arm, which is mounted directly on the setting device. The moving coil system, the balance arm, the nozzle/impact-plate system as well as the position report from the stroke output of the setting device via the spring form an electropneumatic follow-on mechanism with which the result is to be obtained that the setting stroke is proportional to the current fed into the moving coil system. This electropneumatic position regulator has the disadvantage that it is necessary to mount the vibration-sensitive parts, namely the current/pressure transducer with the nozzle/impact-plate system directly on the setting device.
By this arrangement disturbing variables, namely mechanical blows and vibrations which come from the setting device or are transferred by it, can be coupled into the nozzle/impact-plate system. Furthermore, the follow-on mechanism cannot be adapted in simple manner to the setting stroke of the setting device since the setting stroke is transferred as force to the balance arm. For adaptation, different springs or more complicated setting means would have to be provided, depending on the setting stroke provided.